Comparative Assessment of Impacts of Future Climate Change on Runoff in Upper Daqinghe Basin, China

Assessing runoff changes is of great importance especially its responses to the projected future climate change on local scale basins because such analyses are generally done on global and regional scales which may lead to generalized conclusions rather than specific ones. Climate change affected the runoff variation in the past in the upper Daqinghe Basin, however, the climate was mainly considered uncertain and still needs further studies, especially its future impacts on runoff for better water resources management and planning. Integrated with a set of climate simulations, a daily conceptual hydrological model (MIKE11-NAM) was applied to assess the impact of climate change on runoff conditions in the Daomaguan, Fuping and Zijingguan basins in the upper Daqinghe Basin. Historical hydrological data (2008-2017) were used to evaluate the applicability of the MIKE11-NAM model. After bias correction, future projected climate change and its impacts on runoff (2025-2054) were analysed and compared to the baseline period (1985-2014) under three shared social economic pathways (SSP1-2.6, SSP2-4.5, and SSP5-8.5) scenarios from Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations. The MIKE-11 NAM model was applicable in all three Basins, with both R2 and Nash-Sutcliffe Efficiency coefficients greater than 0.6 at daily scale for both calibration (2009-2011) and validation (2012-2017) periods, respectively. Although uncertainties remain, temperature and precipitation are projected to increase compared to the baseline where higher increases in precipitation and temperature are projected to occur under SSP2-4.5 and SSP5-8.5 scenarios, respectively in all the basins. Precipitation changes will range between 12%-19% whereas temperature change will be 2.0 degrees C-2.5 degrees C under the SSP2-4.5 and SSP5-8.5 scenarios, respectively. In addition, higher warming is projected to occur in colder months than in warmer months. Overall, the runoff of these three basins is projected to respond to projected climate changes differently because runoff is projected to only increase in the Fuping basin under SSP2-4.5 whereas decreases in both Daomaguan and Zijingguan Basins under all scenarios. This study's findings could be important when setting mitigation strategies for climate change and water resources management.